Effect of Training Intensity on Microvascular Function

Muscle tissue samples obtained from the vastus lateralis were processed using optical clearing and immunohistochemical staining techniques to visualize the microvascular network. Confocal microscopy was employed to acquire high-resolution three-dimensional images of arterioles, capillaries, and venules. Quantitative assessments included:

• Internal diameter measurements, based on endothelial cell boundaries (intima layer)
• External diameter measurements, based on smooth muscle cells and pericytes (media layer)
• Capillary density, determined by counting the number of capillaries per sample volume

VO₂max was determined using a graded, incremental exercise test performed on a cycle ergometer until volitional exhaustion. Throughout the test, respiratory gases were continuously measured using a metabolic cart (e.g., COSMED K5), which provided breath-by-breath analysis.

The following parameters were recorded :

• VO₂ (oxygen uptake) in mL/min
• VCO₂ (carbon dioxide production) in mL/min
• Minute ventilation (VE) in L/min

Innocor is a medical device that estimates cardiac output using the inert gas rebreathing technique, a validated non-invasive method. During the procedure, the participant inhales a gas mixture containing nitrous oxide (N₂O) and sulfur hexafluoride (SF₆) through a closed circuit. These inert gases are absorbed and eliminated at rates proportional to pulmonary blood flow. By analyzing the washout kinetics of these gases during a brief rebreathing period, Innocor calculates pulmonary blood flow, which is then used to estimate cardiac output. This measurement is typically performed at rest or at peak exercise intensity, such as during the final stage of a cardiopulmonary exercise test (CPET).

The system provides real-time data on:

• Cardiac output (L/min)
• Stroke volume (ml/min)
• Heart rate (bpm)
• Pulmonary blood flow (L/min)